The multifunctional Ccr4–Not complex directly promotes transcription elongation

Abstract

The Ccr4-Not complex has been implicated in the control of multiple steps of mRNA metabolism; however, its functions in transcription remain ambiguous. The discovery that Ccr4/Pop2 is the major cytoplasmic mRNA deadenylase and the detection of Not proteins within mRNA processing bodies have raised questions about the roles of the Ccr4-Not complex in transcription. Here we firmly establish Ccr4-Not as a positive elongation factor for RNA polymerase II (RNAPII). The Ccr4-Not complex is targeted to the coding region of genes in a transcription-dependent manner similar to RNAPII and promotes elongation in vivo. Furthermore, Ccr4-Not interacts directly with elongating RNAPII complexes and stimulates transcription elongation of arrested polymerase in vitro. Ccr4-Not can reactivate backtracked RNAPII using a mechanism different from that of the well-characterized elongation factor TFIIS. While not essential for its interaction with elongation complexes, Ccr4-Not interacts with the emerging transcript and promotes elongation in a manner dependent on transcript length, although this interaction is not required for it to bind RNAPII. Our comprehensive analysis shows that Ccr4-Not directly regulates transcription, and suggests it does so by promoting the resumption of elongation of arrested RNAPII when it encounters transcriptional blocks in vivo.

Comparative dynamic transcriptome analysis (cDTA) reveals mutual feedback between mRNA synthesis and degradation

“…The Pol II subcomplex Rpb4/7 shuttles between the nucleus and cytoplasm (Selitrennik et al 2006) and is involved in transcription (Edwards et al 1991) and mRNA translation and degradation (Lotan et al 2005;Lotan et al 2007;Harel-Sharvit et al 2010). The Ccr4-Not complex is involved in mRNA degradation (Tucker et al 2002) and also in transcription (Liu et al 1998;Collart 2003;Collart and Timmers 2004;Kruk et al 2011). From an extension of our kinetic model of mRNA turnover, we propose that the feedback loop is established by a factor that acts as degradation enhancer and a transcription inhibitor.…”

The Rpb4/7 Module of RNA Polymerase II Is Required for Carbon Catabolite Repressor Protein 4-Negative on TATA (Ccr4-Not) Complex to Promote Elongation

“…Ccr4 resides in a multisubunit complex called Ccr4-Not, which was first described as a transcriptional activator/ repressor (9,12). In addition to regulating the TATA-binding protein at the initiation stage, it directly associates with elongating RNA polymerase II (RNAPII) 2 and can reactivate arrested polymerase in vitro (13,14). Ccr4-Not has pivotal roles in both mRNA production and decay.…”

Post-Transcriptional Regulation of DNA Damage-Responsive Gene Expression

“…BTG2 interacts with the CNOT7 and CNOT8 subunits of the CCR4-NOT deadenylase complex and facilitates deadenylation of mRNAs (32,33,99,100,163). As indicated earlier, the orthologous complex in yeast contributes to the synthesis and decay of mRNAs (113), so the BTG2-CCR4-NOT complex may similarly affect various stages in mRNA synthesis and maturation as well (70,81). It is likely that other UV-responsive RBPs have yet to be identified.…”